Electrically conductive coatings comprising fluorinated carbon filled fluoroelastomer

ABSTRACT

A coating or layer containing a fluorinated carbon filled fluoroelastomer wherein the resistivity of the fluorinated carbon filled fluoroelastomer is controlled. Specifically, the coating comprises fluorinated carbon and polymer component selected from vinylidenefluoride/hexafluoropropylene/tetrafluoroethelene/cure site monomer rubber and volume grafted fluoroelastomers.

CROSS REFERENCE TO RELATED APPLICATIONS

Attention is directed to the following copending applications assignedto the assignee of the present application: U.S. application Ser. No.08/672,803 filed Jun. 24, 1996, entitled, "Biasable Charging Members;"U.S. application Ser. No. 08/635,356 filed Apr. 16, 1996, entitled,"Biasable Transfer Members;" Attorney Docket No. D/95610, U.S.application Ser. No. 08/786,614 filed Jan. 21, 1997, entitled, "OhmicContact-Providing Compositions;" U.S. application Ser. No. 08/706,057filed Aug. 28, 1996, entitled, "Fixing Apparatus and Film;" U.S.application Ser. No. 08/706,387 filed Aug. 28, 1996, entitled, "InstantOn Fuser System Members;" Attorney Docket No. D/95632, U.S. applicationSer. No. 08/779,287 filed Jan 21, 1997, entitled, "Intermediate TransferMembers;" and Attorney Docket No. D/96605Q, U.S. application Ser. No.08/808,765 filed Mar 3, 1997, entitled, "Electrically ConductiveProcesses." The disclosures of each of these applications are herebyincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to electrically conductive coatings, andmore specifically, to electrically conductive coatings useful ascoatings or layers for components for electrical applications,especially electrostatographic applications such as xerographicapplications. In embodiments of the present invention, there areselected electrically conductive coatings or layers comprising a polymerfilled with an electrically conductive material. In a preferredembodiment, the polymer is a fluoropolymer, and particularly preferred afluoroelastomer, and the preferred filler is a fluorinated carbon. Inembodiments, the present invention allows for the preparation andmanufacture of coatings or layers for xerographic components, thecoatings and layers having excellent electrical, chemical and mechanicalproperties, including controlled resistivity in a desired resistivityrange. Further, in embodiments, the coatings and layers exhibitexcellent chemical and electrical properties such as statisticalinsensitivity of resistivity to increases in temperature and toenvironmental changes.

In a typical electrostatographic reproducing apparatus, a light image ofan original to be copied is recorded in the form of an electrostaticlatent image upon a photosensitive member and the latent image issubsequently rendered visible by the application of electroscopicthermoplastic resin particles which are commonly referred to as toner.Generally, the electrostatic latent image is developed by bringing adeveloper mixture into contact therewith. A dry developer mixtureusually comprises carrier granules having toner particles adheringtriboelectrically thereto. Toner particles are attracted from thecarrier granules to the latent image forming a toner powder imagethereon. Alternatively, a liquid developer material may be employed. Theliquid developer material includes a liquid carrier having tonerparticles dispersed therein. The liquid developer material is advancedinto contact with the electrostatic latent image and the toner particlesare deposited thereon in image configuration. After the toner particleshave been deposited on the photoconductive surface, in imageconfiguration, it is transferred to a substrate such as a copy sheet.The toner image is usually fixed or fused upon a support which may bethe photosensitive member itself or other support sheet such as plainpaper.

Because there is required numerous transfers and fixation of chargedtoner particles by various components in the xerographic process, it isdesired to provide components with layers that allow for the chargedparticles to be exchanged from component to component or from componentto substrate (in the case of fusing toner to a substrate such as paper)with near 100% transfer efficiency. In order to help decrease chargeexchange and increase toner transfer efficiency, the resistivity of thecomponents must be within a desired range, and preferably, theresistivity should be virtually unaffected to changes in humidity,temperature and operating time. Attempts at controlling the resistivityof various components have been accomplished by, for example, addingconductive fillers such as ionic additives and/or carbon black to thecomponent layers.

U.S. Pat. No. 5,537,195 discloses an intermediate transfer member foruse with liquid developers, wherein the intermediate transfer membercomprises a fluorocarbon elastomer with metal oxide fillers therein.

U.S. Pat. No. 5,525,446 discloses an intermediate transfer member foruse with color systems which includes a base layer and a toppolycarbonate layer, wherein the top layer can include electricalproperty regulating materials such as metal oxides or carbon black.

U.S. Pat. No. 5,456,987 discloses an intermediate transfer component forboth dry and liquid toner, comprising a substrate and a coatingcomprised of integral, interpenetrating networks of haloelastomer,titanium oxide and optionally polyorganosiloxane, wherein the substratemay include dielectric or conductive fillers such as carbon or metaloxide particles.

U.S. Pat. No. 5,084,738 discloses use of a resistive heating layer withresistivity ranging from 20 to 2000 ohm-cm in a fusing apparatus. Theresistivity of the layer is achieved by adding conductive carbon fillersinto a polymer layer.

U.S. Pat. No. 5,112,708 to Okunuki et al. discloses a charging membercomprising a surface layer formed of N-alkoxymethylated nylon which maybe filled with fluorinated carbon.

While addition of electrically conductive additives to polymers maypartially control the resistivity of polymer coatings or layers to someextent, there are problems associated with the use of these additives,such as problems with non-uniform dispersity. In particular, undissolvedparticles frequently bloom or migrate to the surface of the polymer andcause an imperfection in the polymer. This leads to a nonuniformresistivity, which in turn, leads to poor antistatic properties and poormechanical strength. The ionic additives on the surface may interferewith toner release and affect toner offset. Furthermore, bubbles appearin the conductive polymer, some of which can only be seen with the aidof a microscope, others of which are large enough to be observed withthe naked eye. These bubbles provide the same kind of difficulty as theundissolved particles in the polymer namely, poor or nonuniformelectrical properties and poor mechanical properties.

In addition, the ionic additives themselves are sensitive to changes intemperature, humidity, and operating time. For the vast majority ofconductive particle filled systems, there is observed a percolationthreshold or concentration range in which the resistivity of the filledpolymer will change by many orders of magnitude over a smallconcentration. These sensitivities often limit the resistivity range.For example, the resistivity usually decreases by up to two orders ofmagnitude or more as the humidity increases from 20% to 80% relativehumidity. This effect limits the operational or process latitude.

Moreover, ion transfer can also occur in these systems. The transfer ofions will lead to charge exchanges and insufficient transfers, which inturn, will cause low image resolution and image deterioration, therebyadversely affecting the copy quality. In color systems, additionaladverse results are color shifting and color deterioration. Ion transferalso increases the resistivity of the polymer coating or layer afterrepetitive use. This can limit the process and operational latitude andeventually the ion-filled polymer component will be unusable.

Carbon black particles can impart other specific adverse effects. Suchcarbon dispersions are difficult to prepare due to carbon gelling, andthe resulting layers may deform due to gelatin formation. This can leadto an adverse change in the conformability of the layer, which in turn,can lead to insufficient transfer and poor copy quality, and possiblecontamination of other machine parts and later copies.

Generally, carbon additives tend to control the resistivities andprovide somewhat stable resistivities upon changes in temperature,relative humidity, running time, and leaching out of contamination tophotoconductors. However, the required tolerance in the filler loadingto achieve the required range of resistivity has been extremely narrow.This, along with the large "batch to batch" variation, leads to the needfor extremely tight resistivity control. In addition, carbon filledpolymer surfaces have typically had very poor dielectric strength andsometimes significant resistivity dependence on applied fields. Thisleads to a compromise in the choice of centerline resistivity due to thevariability in the electrical properties, which in turn, ultimatelyleads to a compromise in performance.

Therefore, there exists an overall need for compositions useful ascoatings or layers for xerographic components, which provide forincreased toner transfer efficiency and a decrease in the occurrence ofcharge exchange or toner offset. More specifically, there exists aspecific need for a composition useful as coatings or layers forxerographic components, wherein the layers having controlled resistivityin a desired range so as to neutralize toner charges, thereby decreasingthe occurrence of charge exchange or toner offset, increasing imagequality and preventing contamination of other xerographic members.

SUMMARY OF THE INVENTION

Examples of objects of the present invention include:

It is an object of the present invention to provide compositions usefulas coatings and layers, and methods thereof with many of the advantagesindicated herein.

Further, it is an object of the present invention to provide a coatingwhich has superior electrical properties including a stable resistivityin the desired resistivity range.

It is another object of the present invention to provide a coating witha controlled resistivity which is virtually unaffected by changes inhumidity.

Yet another object of the present invention is to provide a coating witha controlled resistivity which is virtually unaffected by changes intemperature.

Another object of the present invention is to provide a coating with acontrolled resistivity which is virtually unaffected by changes inapplied electric field.

A further object of the present invention is to provide a coating whichpossesses a decreased hysteresis effect.

A still further object of the present invention is to provide a coatingwhich provides more uniform dispersity of conductive filler within thecoating.

The present invention includes, in embodiments: a coating comprising afluorinated carbon filled fluoroelastomer.

Embodiments further include: a coating comprising a fluorinated carbonfilled fluoroelastomer, wherein the fluoroelastomer is selected from thegroup consisting of a) copolymers of vinylidenefluoride,hexafluoropropylene and tetrafluoroethylene, b) terpolymers ofvinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, and c)tetrapolymers of vinylidenefluoride, hexafluoropropylene,tetrafluoroethylene and a cure site monomer, and wherein the fluorinatedcarbon is of the formula CF_(x), wherein x represents the number offluorine atoms and is, for example, from about 0.02 to about 1.5.

In addition, embodiments include: a coating comprising a fluorinatedcarbon filled fluoroelastomer, wherein the coating has a controlledresistivity, and in preferred embodiments, the coating has a firstresistivity and a second resistivity, wherein the first resistivity is aresistivity of the coating at room temperature for example about 25° C.,and wherein the second resistivity is a resistivity of the coating upona change in temperature, wherein the second resistivity remains withinabout 50 to about 100% of the first resistivity at a temperature rangeof from about 0° to about 200° C.; and in another preferred embodiment,the coating has a first resistivity and a second resistivity, whereinthe first resistivity is a resistivity of the coating at ambientrelative humidity for example about 50%, and wherein the secondresistivity is a resistivity of the coating upon a change in relativehumidity, wherein the second resistivity remains within about 50 toabout 100% of the first resistivity at a relative humidity range of fromabout 0% to about 80% relative humidity.

The coatings and layers herein, in embodiments, enable control ofdesired resistivities, allow for uniform electrical properties includingresistivity, and neutralize toner charges, all of which contribute togood release properties, a decrease in the occurrence of chargeexchange, a decrease in the occurrence of toner offset, an increase inimage quality, and a decrease in contamination of other xerographiccomponents such as photoconductors. The coatings and layers providedherein, in embodiments, also have improved insensitivities toenvironmental and mechanical changes.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The present invention relates to coatings and layers comprising afluorinated carbon filled fluoroelastomer. These coatings and layers areuseful as layers for components useful in electrical applications, suchas xerographic applications. The resistivity of the layers or coatingsis essential for proper and efficient performance of the components.Depending on the function of the component and process speed of theapparatus, the electrical requirements for the coatings are different.Generally, the desired volume resistivity of the coatings is from about10² to about 10¹⁴ ohm-cm, and the desired surface resistivity is fromabout 10² to about 10¹⁴ ohm/sq, for many xerographic components. Thepreferred volume resistivity for most xerographic systems is from about10³ to about 10¹² ohm-cm and the preferred surface resistivity is fromabout 10³ to about 10¹² ohm/sq. Examples of preferred resistivity rangesfor various components are as follows. For example, the preferredresistivity range for an intermediate transfer belt surface is fromabout 10⁴ to about 10¹² ohm-cm; the desired volume resistivity for ascavengeless development electrode donor member overcoat is about 10⁹ohm-cm; the conductive core for a bias charging roll has a desiredvolume resistivity of from about 10³ to about 10¹² ohm-cm; the preferredresistivity of a donor roll coating is from about 10⁶ to about 10¹² ;while the preferred resistivity of an overcoat for a bias chargingmember is from about 10³ to about 10¹⁰ ohm-cm.

A fluoroelastomer in combination with a fluorinated carbon fillerdispersed therein, provides superior results by allowing, for example, aresistivity within a specific range desired for the specificapplication, wherein the resistivity is virtually unaffected byenvironmental changes such as changes in humidity and temperature, ormechanical changes such as changes in the electrical charge or fieldassociated with the component. This controlled resistivity is animportant and superior feature of the present invention.

More specifically, although with known coatings, a change in temperatureor a change in humidity can cause a severe change in the resistivity ofthe coating, the coatings of the present invention are much lessreactive to environmental changes. The coatings comprising fluorinatedcarbon filled fluoroelastomers have controlled resistivity. For example,the resistivity usually decreases by up to two orders of magnitude ormore as the humidity increases from 20% to 80% relative humidity. Thiseffect limits the operational or process latitude. However, withfluorinated carbon filled fluoroelastomers, the resistivity of thecoating is controlled and will remain within the desired range of 10² toabout 10¹⁴ ohms-cm, or the preferred range of from about 10³ to about10¹⁴ ohms-cm, at broad temperatures ranging from about 0° C. to about200° C., and/or at broad humidity ranges of 0 to about 80% relativehumidity. In preferred embodiments, the desired resistivity will remainwithin from about 50 to about 100% of the original desired resistivityrange upon a temperature range of from about 0° C. to about 200° C.,and/or will remain within from about 50 to about 100% of the desiredresistivity range upon a change in relative humidity of from about 0 toabout 80% relative humidity. The original desired resistivity is thedesired resistivity which is measured at room temperature, or about 25°C., and at ambient relative humidity, or about 50% relative humidity.This desired resistivity will be a resistivity chosen for a particularcoating for a specific component. The desired resistivity will varydepending on the component and the desired qualities, performance anduse of the component. In addition to remaining stable upon broad changesin temperature and relative humidity, the controlled resistivity isvirtually unaffected by exposure of the coating to corona affluent.

Using fluorinated carbon as a filler in fluoroelastomers which areformed into coatings or layers for components useful in xerographicapplications helps to solve the problems related to incomplete tonertransfer from component to component or hot offset caused by toner fromthe substrate adhering to the fusing surface. The coatings and layers inaccordance with the present invention, enable high yield transfer oftoner particles from the various component members due to thecombination of fluorinated carbon and fluoroelastomer which, incombination, provide for a stable resistivity within the desired range.Further, such fluorinated carbon filled fluoroelastomers greatly reducethe charge exchange between the components, or between the componentsand a substrate.

The particular resistivity of the fluoropolymer composition can bechosen and controlled depending, for example, on the amount offluorinated carbon, the nature of the curative, the amount of curative,the amount of fluorine in the fluorinated carbon, and the curingprocedures including the specific curing agent such as for example MgO,CaO, and Ca(OH)₂, curing time, and curing temperature. The resistivitycan be generated not only by selecting the appropriate curing agents,curing time and curing temperature as set forth above, but also byselecting a specific polymer and filler, such as a specific fluorinatedcarbon, or mixtures of various types of fluorinated carbon. Thepercentage of fluorine in the fluorinated carbon will also affect theresistivity of the fluoroelastomer when mixed therewith.

Fluorinated carbon, sometimes referred to as graphite fluoride or carbonfluoride, is a solid material resulting from the fluorination of carbonwith elemental fluorine. The number of fluorine atoms per carbon atommay vary depending on the fluorination conditions. The variable fluorineatom to carbon atom stoichiometry of fluorinated carbon permitssystemic, uniform variation of its electrical resistivity properties.

Fluorinated carbon refers to a specific class of compositions which isprepared by reacting fluorine to one or more of the many forms of solidcarbon. In addition, the amount of fluorine can be varied in order toproduce a specific, desired resistivity. Fluorocarbons are eitheraliphatic or aromatic organic compounds wherein one or more fluorineatoms have been attached to one or more carbon atoms to form welldefined compounds with a single sharp melting point or boiling point.Fluoropolymers are linked-up single identical molecules which compriselong chains bound together by covalent bonds. Moreover, fluoroelastomersare a specific type of fluoropolymer. Thus, despite some apparentconfusion in the art, it is apparent that fluorinated carbon is neithera fluorocarbon nor a fluoropolymer and the term is used in this contextherein.

The fluorinated carbon may include the fluorinated carbon materials asdescribed herein. The methods for preparation of fluorinated carbon arewell known and documented in the literature, such as in the followingU.S. Pat. Nos. 2,786,874; 3,925,492; 3,925,263; 3,872,032 and 4,247,608,the disclosures each of which are totally incorporated by referenceherein. Essentially, fluorinated carbon is produced by heating a carbonsource such as amorphous carbon, coke, charcoal, carbon black orgraphite with elemental fluorine at elevated temperatures, such as150°-600° C. A diluent such as nitrogen is preferably admixed with thefluorine. The nature and properties of the fluorinated carbon vary withthe particular carbon source, the conditions of reaction and with thedegree of fluorination obtained in the final product. The degree offluorination in the final product may be varied by changing the processreaction conditions, principally temperature and time. Generally, thehigher the temperature and the longer the time, the higher the fluorinecontent.

Fluorinated carbon of varying carbon sources and varying fluorinecontents is commercially available from several sources. Preferredcarbon sources are carbon black, crystalline graphite and petroleumcoke. One form of fluorinated carbon which is suitable for use inaccordance with the invention is polycarbon monofluoride which isusually written in the shorthand manner CF_(x) with x representing thenumber of fluorine atoms and generally being up to about 1.5, preferablyfrom about 0.01 to about 1.5, and particularly preferred from about 0.04to about 1.4. The formula CF_(x) has a lamellar structure composed oflayers of fused six carbon rings with fluorine atoms attached to thecarbons and lying above and below the plane of the carbon atoms.Preparation of CF_(x) type fluorinated carbon is described, for example,in above-mentioned U.S. Pat. Nos. 2,786,874 and 3,925,492, thedisclosures of which are incorporated by reference herein in theirentirety. Generally, formation of this type of fluorinated carboninvolves reacting elemental carbon with F₂ catalytically. This type offluorinated carbon can be obtained commercially from many vendors,including Allied Signal, Morristown, N.J.; Central Glass International,Inc., White Plains, N.Y.; Diakin Industries, Inc., New York, N.Y.; andAdvance Research Chemicals, Inc., Catoosa, Okla.

Another form of fluorinated carbon which is suitable for use inaccordance with the invention is that which has been postulated byNobuatsu Watanabe as poly(dicarbon monofluoride) which is usuallywritten in the shorthand manner (C₂ F)_(n). The preparation of (C₂F)_(n) type fluorinated carbon is described, for example, inabove-mentioned U.S. Pat. No. 4,247,608, the disclosure of which isherein incorporated by reference in its entirety, and also in Watanabeet al., "Preparation of Poly(dicarbon monofluoride) from PetroleumCoke", Bull. Chem. Soc. Japan, 55, 3197-3199 (1982), the disclosure ofwhich is also incorporated herein by reference in its entirety.

In addition, preferred fluorinated carbons selected include thosedescribed in U.S. Pat. No. 4,524,119 to Luly et al., the subject matterof which is hereby incorporated by reference in its entirety, and thosehaving the tradename ACCUFLUOR®, (ACCUFLUOR® is a registered trademarkof Allied Signal, Morristown, N.J.) for example, ACCUFLUOR® 2028,ACCUFLUOR® 2065, ACCUFLUOR® 1000, and ACCUFLUOR® 2010. ACCUFLUOR® 2028and ACCUFLUOR® 2010 have 28 and 11 percent fluorine content,respectively. ACCUFLUOR® 1000 and ACCUFLUOR® 2065 have 62 and 65 percentfluorine content respectively. Also, ACCUFLUOR® 1000 comprises carboncoke, whereas ACCUFLUOR® 2065, 2028 and 2010 all comprise conductivecarbon black. These fluorinated carbons are of the formula CF_(x) andare formed by the reaction of C+F₂ =CF_(x).

The following chart illustrates some properties of four fluorinatedcarbons of the present invention.

    ______________________________________                                        PROPERTIES   ACCUFLUOR ®  UNITS                                           ______________________________________                                        GRADE        1000   2065    2028 2010 N/A                                     Feedstock    Coke   Conductive Carbon                                                                           N/A                                                             Black                                                     Fluorine Content                                                                           62     65      28   11   %                                       True Density 2.7    2.5     2.1  1.9  g/cc                                    Bulk Density 0.6    0.1     0.1  0.09 g/cc                                    Decomposition Tempera-                                                                     630    500     450  380  °C.                              ture                                                                          Median Particle Size                                                                       8      <1      <1   <1   micrometers                             Surface Area 130    340     130  170  m.sup.2 /g                              Thermal Conductivity                                                                       10.sup.-3                                                                            10.sup.-3                                                                             10.sup.-3                                                                          N.A. cal/cm-sec-°C.                   Electrical Resistivity                                                                     10.sup.11                                                                            10.sup.11                                                                             10.sup.8                                                                           <10  ohm-cm                                  Color        Gray   White   Black                                                                              Black                                                                              N/A                                     ______________________________________                                    

As has been described herein, a major advantage of the invention is thecapability to vary the fluorine content of the fluorinated carbon topermit systematic uniform variation of the resistivity properties of thecomposition or layer. The preferred fluorine content will depend on,inter alia, the equipment used, equipment settings, desired resistivity,and the specific fluoroelastomer chosen. The fluorine content in thefluorinated carbon is from about 1 to about 70 weight percent based onthe weight of fluorinated carbon (carbon content of from about 99 toabout 30 weight percent), preferably from about 5 to about 65 (carboncontent of from about 95 to about 35 weight percent), and particularlypreferred from about 10 to about 30 weight percent (carbon content offrom about 90 to about 70 weight percent).

The median particle size of the fluorinated carbon can be less than 1micron and up to 10 microns, is preferably less than 1 micron,preferably from about 0.001 to about 1 microns, and particularlypreferred from about 0.5 to 0.9 micron. The surface area is preferablyfrom about 100 to about 400 m² /g, preferred of from about 110 to about340, and particularly preferred from about 130 to about 170 m² /g. Thedensity of the fluorinated carbons is preferably from about 1.5 to about3 g/cc, preferably from about 1.9 to about 2.7 g/cc.

The amount of fluorinated carbon in the layer is from about 1 to about50 percent by weight of the total solids content, preferably from about1 to about 40 weight percent, and particularly preferred from about 5 toabout 30 weight percent based on the weight of total solids. Totalsolids as used herein refers to the amount of fluoroelastomer and/orother elastomers.

It is preferable to mix different types of fluorinated carbon to tunethe mechanical and electrical properties. It is desirable to usemixtures of different kinds of fluorinated carbon to achieve goodresistivity while reducing the hardness of the coating. Also, mixturesof different kinds of fluorinated carbon can provide an unexpected wideformulation latitude and controlled and predictable resistivity. Forexample, an amount of from about 0 to about 40 percent, preferably fromabout 1 to about 40, and particularly preferred of from about 5 to about35 percent by weight of ACCUFLUOR® 2010 can be mixed with an amount offrom about 0 to about 40 percent, preferably from about 1 to about 40,and particularly preferred from about 5 to about 35 percent ACCUFLUOR®2028, and even more particularly preferred from about 8 to about 25percent ACCUFLUOR® 2028. Other forms of fluorinated carbon can also bemixed. Another example is an amount of from about 0 to about 40 percentACCUFLUOR® 1000, and preferably from about 1 to about 40 percent, andparticularly preferred from about 5 to about 35 percent, mixed with anamount of from about 0 to about 40 percent, preferably from about 1 toabout 40, and particularly preferred from about 1 to about 35 percentACCUFLUOR® 2065. All other combinations of mixing the different forms ofACCUFLUOR® are possible. A preferred mixture is from about 0 to about 15percent ACCUFLUOR® 2028 mixed with from about 2 to about 3.5 percentACCUFLUOR® 2010. Another preferred mixture is from about 0.5 to about 10percent ACCUFLUOR® 2028 mixed with from about 2.0 to about 3.0 percentACCUFLUOR® 2010. A particularly preferred mixture is from about 1 toabout 3 percent ACCUFLUOR® 2028 mixed with from about 2.5 to about 3percent ACCUFLUOR® 2010, and even more preferred is a mixture of about 3percent ACCUFLUOR® 2010 and about 2 percent ACCUFLUOR® 2028. All theabove percentages are by weight of the total solids.

The fluorinated carbon is preferably dispersed in a polymer. Examples ofsuitable polymers include fluoropolymers and particularly,fluoroelastomers. Specifically, suitable fluoroelastomers are thosedescribed in detail in U.S. Pat. Nos. 5,166,031, 5,281,506, 5,366,772and 5,370,931, together with U.S. Pat. Nos. 4,257,699, 5,017,432 and5,061,965, the disclosures each of which are incorporated by referenceherein in their entirety. As described therein these fluoroelastomers,particularly from the class of copolymers and terpolymers ofvinylidenefluoride, hexafluoropropylene and tetrafluoroethylene, areknown commercially under various designations as VITON® A, VITON® E,VITON® E60C, VITON® E430, VITON® 910, VITON® GH and VITON® GF. TheVITON® designation is a Trademark of E. I. DuPont de Nemours, Inc. Othercommercially available materials include FLUOREL® 2170, FLUOREL® 2174,FLUOREL® 2176, FLUOREL® 2177 and FLUOREL® LVS 76. FLUOREL® is aTrademark of 3M Company. Additional commercially available materialsinclude AFLAS™ a poly(propylene-tetrafluoroethylene) and FLUOREL II®(LII900) a poly(propylene-tetrafluoroethylenevinylidenefluoride) bothalso available from 3M Company, as well as the Tecnoflons identified asFOR-60KIR®, FOR-LHF®, NM® FOR-THF®, FOR-TFS®, TH®, TN505® available fromMontedison Specialty Chemical Company. In another preferred embodiment,the fluoroelastomer is one having a relatively low quantity ofvinylidenefluoride, such as in VITON® GF, available from E. I. DuPont deNemours, Inc. The VITON® GF has 35 mole percent of vinylidenefluoride,34 mole percent of hexafluoropropylene and 29 mole percent oftetrafluoroethylene with 2 percent cure site monomer. The cure sitemonomer can be 4-bromoperfluorobutene-1,1,1-dihydro-4-bromoperfluorobutene-1, 3-bromoperfluoropropene-1,1,1-dihydro-3-bromoperfluoropropene-1, available from DuPont, or anyother suitable, known cure site monomer.

Examples of fluoroelastomers suitable for use herein include elastomersof the above type, along with volume grafted elastomers. Volume graftedelastomers are a special form of hydrofluoroelastomer and aresubstantially uniform integral interpenetrating networks of a hybridcomposition of a fluoroelastomer and a polyorganosiloxane, the volumegraft having been formed by dehydrofluorination of fluoroelastomer by anucleophilic dehydrofluorinating agent, followed by additionpolymerization by the addition of an alkene or alkyne functionallyterminated polyorganosiloxane and a polymerization initiator. Examplesof specific volume graft elastomers are disclosed in U.S. Pat. No.5,166,031; U.S. Pat. No. 5,281,506; U.S. Pat. No. 5,366,772; and U.S.Pat. No. 5,370,931, the disclosures each of which are hereinincorporated by reference in their entirety.

Volume graft, in embodiments, refers to a substantially uniform integralinterpenetrating network of a hybrid composition, wherein both thestructure and the composition of the fluoroelastomer andpolyorganosiloxane are substantially uniform when taken throughdifferent slices of the layers of the member. A volume grafted elastomeris a hybrid composition of fluoroelastomer and polyorganosiloxane formedby dehydrofluorination of fluoroelastomer by nucleophilicdehydrofluorinating agent followed by addition polymerization by theaddition of alkene or alkyne functionally terminated polyorganosiloxane.

Interpenetrating network, in embodiments, refers to the additionpolymerization matrix where the fluoroelastomer and polyorganosiloxanepolymer strands are intertwined in one another.

Hybrid composition, in embodiments, refers to a volume graftedcomposition which is comprised of fluoroelastomer and polyorganosiloxaneblocks randomly arranged.

Generally, the volume grafting according to the present invention isperformed in two steps, the first involves the dehydrofluorination ofthe fluoroelastomer preferably using an amine. During this step,hydrofluoric acid is eliminated which generates unsaturation, carbon tocarbon double bonds, on the fluoroelastomer. The second step is the freeradical peroxide induced addition polymerization of the alkene or alkyneterminated polyorganosiloxane with the carbon to carbon double bonds ofthe fluoroelastomer. In embodiments, copper oxide can be added to asolution containing the graft copolymer. The dispersion is then providedonto the substrate or conductive film surface.

In embodiments, the polyorganosiloxane having functionality according tothe present invention has the formula: ##STR1## where R is an alkyl fromabout 1 to about 24 carbons, or an alkenyl of from about 2 to about 24carbons, or a substituted or unsubstituted aryl of from about 4 to about18 carbons; A is an aryl of from about 6 to about 24 carbons, asubstituted or unsubstituted alkene of from about 2 to about 8 carbons,or a substituted or unsubstituted alkyne of from about 2 to about 8carbons; and n represents the number of segments and is, for example,from about 2 to about 400, and preferably from about 10 to about 200 inembodiments.

In preferred embodiments, R is an alkyl, alkenyl or aryl, wherein alkylcontains from about 1 to about 24 carbons, preferably from about 1 toabout 12 carbons; the alkenyl contains from about 2 to about 24 carbons,preferably from about 2 to about 12 carbons; and the aryl contains fromabout 6 to about 24 carbon atoms, preferably from about 6 to about 18carbons. R may be a substituted aryl group, wherein the aryl may besubstituted with an amino, hydroxy, mercapto or substituted with analkyl having for example from about 1 to about 24 carbons and preferablyfrom 1 to about 12 carbons, or substituted with an alkenyl having forexample from about 2 to about 24 carbons and preferably from about 2 toabout 12 carbons. In a preferred embodiment, R is independently selectedfrom methyl, ethyl, and phenyl. The functional group A can be an alkeneor alkyne group having from about 2 to about 8 carbon atoms, preferablyfrom about 2 to about 4 carbons, optionally substituted with an alkylhaving for example from about 1 to about 12 carbons, and preferably fromabout 1 to about 12 carbons, or an aryl group having for example fromabout 6 to about 24 carbons, and preferably from about 6 to about 18carbons. Functional group A can also be mono-, di-, or trialkoxysilanehaving from about 1 to about 10 and preferably from about 1 to about 6carbons in each alkoxy group, hydroxy, or halogen. Preferred alkoxygroups include methoxy, ethoxy, and the like. Preferred halogens includechlorine, bromine and fluorine. Group A may also be an alkyne of fromabout 2 to about 8 carbons, optionally substituted with an alkyl of fromabout 1 to about 24 carbons or aryl of from about 6 to about 24 carbons.The group n is a number of from about 2 to about 400, and in embodimentsfrom about 2 to about 350, and preferably from about 5 to about 100.Furthermore, in a preferred embodiment n is from about 60 to about 80,to provide a sufficient number of reactive groups to graft onto thefluoroelastomer. In the above formula, typical R groups include methyl,ethyl, propyl, butyl, pentyl, heptyl, octyl, vinyl, allylic crotnyl,phenyl, naphthyl and phenanthryl, and typical substituted aryl groupsare substituted in the ortho, meta and para positions with lower alkylgroups having from about 1 to about 15 carbon atoms. Typical alkene andalkenyl functional groups include vinyl, acrylic, crotonic and acetenylwhich may typically be substituted with methyl, propyl, butyl, benzyl,tolyl groups, and the like.

In a preferred embodiment of the present invention, the polymer coatingor layer is comprised of a fluorinated carbon filled fluoroelastomer,wherein the fluoroelastomer is VITON® GF and the fluorinated carbon isselected from ACCUFLUOR® 1000, ACCUFLUOR® 2065, ACCUFLUOR® 2028,ACCUFLUOR® 2010, or mixtures thereof.

The amount of fluoroelastomer used to provide the coatings or layers ofthe present invention is dependent on the amount necessary to form thedesired thickness of the coatings or layers. Specifically, thefluoroelastomer is added in an amount of from about 60 to about 99percent, preferably about 70 to about 99 percent by weight of totalsolids.

Any known solvent suitable for dissolving a fluoroelastomer may be usedin the present invention. Examples of suitable solvents for the presentinvention include methyl ethyl ketone, methyl isobutyl ketone, diethylketone, cyclohexanone, n-butyl acetate, amyl acetate, and the like.Specifically, the solvent is added in an amount of from about 25 toabout 99 percent, preferably from about 70 to about 95 percent.

The dehydrofluorinating agent which attacks the fluoroelastomergenerating unsaturation is selected from basic metal oxides such as MgO,CaO, Ca(OH)₂ and the like, and strong nucleophilic agents such asprimary, secondary and tertiary, aliphatic and aromatic amines, wherethe aliphatic and aromatic amines have from about 2 to about 30 carbonatoms. Also included are aliphatic and aromatic diamines and triamineshaving from about 2 to about 30 carbon atoms where the aromatic groupsmay be benzene, toluene, naphthalene, anthracene, and the like. It isgenerally preferred for the aromatic diamines and triamines that thearomatic group be substituted in the ortho, meta and para positions.Typical substituents include lower alkyl amino groups such asethylamino, propylamino and butylamino, with propylamino beingpreferred.

The particularly preferred curing agents are the nucleophilic curingagents such as VITON CURATIVE VC-50® which incorporates an accelerator(such as a quaternary phosphonium salt or salts like VC-20) and acrosslinking agent (bisphenol AF or VC-30); DIAK 1 (hexamethylenediaminecarbamate) and DIAK 3 (N,N'-dicinnamylidene-1,6 hexanediamine). Thedehydrofluorinating agent or curing agent is added in an amount of fromabout 1 to about 20 weight percent, preferably from about 2 to about 10weight percent, and particularly preferred from about 1.5 to about 5weight percent. It has been demonstrated that the curative is importantto providing resistivity in the coating. Specifically, in the absence ofa curative, controlled resistivity is not attained.

Layers or coatings may be formed by forming a coating dispersion bymixing together the fluorinated carbon, fluoroelastomer, solvent andcurative materials, and coating the resulting conductive coatingdispersion on a substrate.

The coatings or layers may be deposited on a substrate via a well knowncoating processes. Known methods for forming coatings or layer(s) on asubstrate include dipping, spraying such as by multiple sprayapplications of very thin films, casting, flow-coating, web-coating,roll-coating, extrusion, molding, or the like. It is preferred todeposit the layers by spraying such as by multiple spray applications ofvery thin films, by web coating or by flow-coating. More than onecoating dispersion of fluorinated carbon filled fluoroelastomer can becoated on a substrate. Multiple layers or coatings can be applied to thesubstrate. For example, from 1 to about 5 layers or coatings can beapplied to the substrate.

The coatings or layers deposited on a substrate are then dried and curedaccording to known curing procedures, including step heat curing. Alower resistivity is obtained when the coatings or layers are cured at ahigher temperature or over a longer period of time. In other words,resistivity has been shown to decrease upon an increase in curingtemperature. Similarly, resistivity has been shown to decrease upon anincrease in curing time.

Preferably, the curing time is about 16 hours and the curing temperatureis from about 25° to about 250° C., and preferably from about 150° toabout 250° C. It has been demonstrated that post-treatment stepsincluding heat-curing step and other current treatments, is important tothe achievement of controlled resistivity. Specifically, in the absenceof heat curing, controlled resistivity is not attained. Therefore, botha curing agent and a heat curing step are important features inproviding controlled resistivity in the fluorinated carbon filledfluoroelastomers.

The mechanism is theorized as follows. It is believed that the startingfluorinated carbon undergoes a defluorination reaction with thefluoroelastomer curative during the fluoroelastomer curing. This resultsin a fluorinated carbon of lesser fluorine content in the binder. It isbelieved that this is the filler that leads to controlled resistivity.It is also possible that during defluorination, the fluorinated carbonmay crosslink with the fluoroelastomer, thereby providing a more stablecomposition.

The coatings and layers, as used herein, can be any layer of anysuitable electrical or mechanical component useful in xerographic orother electrical processes or apparatuses. The layer can be any oneintermediate layer(s), or an outer coating layer of a component.Examples of such xerographic components include intermediate transfermembers, bias charging members, bias transfer members, segmentedelectrode development members, fuser members, donor roll members, imagebearing members, or any other related components.

The polymer coatings and layers comprising a fluorinated carbon filledfluoroelastomer exhibit superior electrical and mechanical properties.The coatings and layers are designed so as to enable control ofelectrical properties including control of resistivity in the desiredresistivity range, wherein the resistivity is virtually insensitive toenvironmental and mechanical changes.

All the patents and applications referred to herein are herebyspecifically, and totally incorporated herein by reference in theirentirety in the instant specification.

The following Examples further define and describe embodiments of thepresent invention. Unless otherwise indicated, all parts and percentagesare by weight.

EXAMPLES Example I

A coating dispersion consisting of ACCUFLUOR® 2028 (from Allied Signal)and VITON® GF (from DuPont) in a weight ratio of 1:3 was prepared in thefollowing manner. About 2,300 g of steel shot and 15 g of ACCUFLUOR®2028 were added to a small bench top attritor (Model 1A), whichcontained 200 g of methyl ethyl ketone (MEK) (from Fisher). The mixturewas gently stirred for about a minute so that the fluorinated carbonparticles became wet due to the solvent. VITON® GF (45 g) was then addedand the resulting mixture attrited for 30 minutes. A curative package2.25 g VC-50 (from DuPont), 0.9 g Maglite-D (from Baker) and 0.2 g(Ca(OH)₂) (from Baker)! and 10 g of a stabilizing solvent, methanol,were introduced and the resulting mixture was then further mixed on theattritor for another 15 minutes. After filtering the steel shot througha wire screen, the dispersion was collected in an 8-oz polypropylenebottle. The resulting dispersion was then coated onto polyimide KAPTON®substrates (from DuPont) and on stainless steel substrates within 2-5hours using a Gardner Laboratory Coater. The coated layers wereair-dried for about 1-2 hours, and then step heat-cured in aprogrammable oven. The heating sequence was as follows: (1) 65° C. for 4hours, (2) 93° C. for 2 hours, (3) 144° C. for 2 hours, (4) 177° C. for2 hours, and (5) 204° C. for 2 hours. The layers were about 2.5 to about3 mil in thickness and were post-cured at 235° C. for 16 hours. Thelayers that resulted were VITON® GF layers containing 25% by weightACCUFLUOR® 2028.

The surface resistivity of the cured VITON® GF layers was measured by aXerox Corporation in-house testing apparatus with of a power supply(Trek 601 C Coratrol), a Keithy electrometer (model 610B), and a twopoint conformable guarded electrode probe (15 mm spacing between the twoelectrodes). The field applied for the measurement was 1500 V/cm and themeasured current was converted to surface resistivity based on thegeometry of the probe. The surface resistivity of the layer wasdetermined to be approximately 1×10¹⁰ ohm/sq.

The volume resistivity of the layer was determined by the standard ACconductivity technique. The surface of the VITON® GF was coated directlyonto a stainless steel substrate, in the absence of an intermediatelayer. An evaporated aluminum thin film (300 Å) was used as the counterelectrode. The volume resistivity was found to be 6×10¹¹ ohm-cm at anelectric field of 1500 V/cm. The resistivity was found to be insensitiveto changes in temperature in the range of about 20° C. to about 150° C.,and to changes in relative humidity in the range of about 20% to about80%, and to the intensity of applied electric field (up to 2,000 V/cm).Furthermore, no hysteresis (memory) effect was seen after the layer wascycled to higher electric fields (>10⁴ V/cm).

Example II

The procedures outlined in Example 1 were repeated except that theloadings of the fluorinated carbon filler ACCUFLUOR® 2028 were variedand ACCUFLUOR® 2010 was also tested. These layers were found to exhibitvery similar electric properties as the layers in Example 1. The resultsare shown below in Table 1.

                  TABLE 1                                                         ______________________________________                                        RESISTIVITY DATA OF FLUORINATED CARBON                                        IN VITON ® GF (FIELD˜1500 V/CM)                                                               Surface   Volume                                    Fluorinated   Loading     Resistivity                                                                             Resistivity                               Carbon        (% by weight)                                                                             (ohm/sq)  (ohm-cm)                                  ______________________________________                                        ACCUFLUOR ® 2028                                                                        35          1.7 × 10.sup.7                                                                    ˜1.6 × 10.sup.8               ACCUFLUOR ® 2028                                                                        30          1.0 × 10.sup.9                                                                    ˜1 × 10.sup.9                 ACCUFLUOR ® 2028                                                                        20          8.9 × 10.sup.11                                                                   ˜2 × 10.sup.13                ACCUFLUOR ® 2010                                                                        30          8.3 × 10.sup.4                                ACCUFLUOR ® 2010                                                                        10          1.9 × 10.sup.5                                ACCUFLUOR ® 2010                                                                        5           4.1 × 10.sup.5                                ACCUFLUOR ® 2010                                                                        3.5         4.5 × 10.sup.6                                ACCUFLUOR ® 2010                                                                        3           1.7 × 10.sup.8                                ______________________________________                                    

Example III

A number of resistive layers were prepared using the dispersing andcoating procedure as described in Example I, with the exception that amixture of various percentages by weight of various types of ACCUFLUOR®were mixed with VITON® GF. The compositions of the ACCUFLUOR® NITON® GFlayers and the surface resistivity results are summarized in Table 2.

                  TABLE 2                                                         ______________________________________                                        Fillers in VITON ® GF                                                                          Surface Resistivity                                      (%)                  (ohm/sq)                                                 ______________________________________                                        2% ACCUFLUOR ® 2010                                                                            4.5 × 10.sup.11                                    15% ACCUFLUOR ® 2028                                                      2.5% ACCUFLUOR ® 2010                                                                          1.0 × 10.sup.9                                     15% ACCUFLUOR ® 2028                                                      3% ACCUFLUOR ® 2010                                                                            5.4 × 10.sup.9                                     5% ACCUFLUOR ® 2028                                                       3% ACCUFLUOR ® 2010                                                                            6.4 × 10.sup.9                                     10% ACCUFLUOR ® 2028                                                      3% ACCUFLUOR ® 2010                                                                            1.3 × 10.sup.10                                    15% ACCUFLUOR ® 2028                                                      3.5% ACCUFLUOR ® 2010                                                                          2 × 10.sup.9                                       5% ACCUFLUOR ® 2028                                                       3.5% ACCUFLUOR ® 2010                                                                          7.2 × 10.sup.9                                     15% ACCUFLUOR ® 2028                                                      ______________________________________                                    

Example IV

Resistive layers containing of 25% by weight of ACCUFLUOR® in VITON® GFwere prepared according to the procedures described in Example I.However, instead of performing a post-curing at 232° C. for 16 hours,the post-curing was performed for 9 hours, 26 hours, 50 hours, 90 hoursand 150 hours, respectively. The surface resistivity results are shownin Table 3.

                  TABLE 3                                                         ______________________________________                                                           Surface Resistivity                                        Post-curing Time   (ohm/sq)                                                   ______________________________________                                         9 hours           5.5 × 10.sup.10                                      26 hours           8.8 × 10.sup.9                                       50 hours           1.8 × 10.sup.9                                       90 hours           7.3 × 10.sup.7                                       150 hours          7.2 × 10.sup.6                                       ______________________________________                                    

Example V

Coating dispersions containing different concentrations of ACCUFLUOR®2010 in VITON® GF were prepared using the attrition procedures given inExample I. These dispersions were then air-sprayed onto KAPTON®substrates. The layers (˜2.5 mil) were air-dried and post-cured usingthe procedure outlined in Example I. The surface resistivity results aresummarized in Table 4 below. The percentages are by weight.

                  TABLE 4                                                         ______________________________________                                        ACCUFLUOR ® 2010                                                                              Surface Resistivity                                       Loading in VITON ® GF (%)                                                                     (ohm/sq)                                                  ______________________________________                                        6%                  1.6 × 10.sup.12                                     7%                  7.0 × 10.sup.8                                      8%                  8.5 × 10.sup.7                                      10%                 6.2 × 10.sup.6                                      20%                 1.1 × 10.sup.5                                      ______________________________________                                    

Example VI

A resistive layer containing of 30% ACCUFLUOR® 2028 in VITON® GF wasprepared according to the procedures described in Example I, with theexception that 4.5 g of curative VC-50 was used. The surface resistivityof the layer was measured using the techniques outlined in Example 1 andwas found to be approximately 5.7×10⁹ ohm/sq.

Example VII

A coating dispersion was prepared by first adding a solvent (200 g ofmethyl ethyl ketone), a steel shot (2,300 g) and 2.4 g of ACCUFLUOR®2028 in a small bench top attritor (model 01A). The mixture was stirredfor about one minute so as to wet the fluorinated carbon with thesolvent. A polymer binder, VITON® GF (45 g), was then added and theresulting mixture was attrited for 30 minutes. A curative package (0.68g DIAK 1 and 0.2 g Maglite Y) and a stabilizing solvent (10 g methanol)were then introduced and the mixture was further mixed for about 15minutes. After filtering the steel shot through a wire screen, thefluorinated carbonNITON® GF dispersion was collected in a polypropylenebottle. The dispersion was then coated onto KAPTON® substrates within2-4 hours using a Gardner laboratory coater. The coated layers werefirst air-dried for approximately two hours and then heat cured in aprogrammable oven. The heating sequence was: (1) 65° C. for 4 hours, (2)93° C. for 2 hours, (3) 144° C. for 2 hours, (4) 177° C. for 2 hours,(5) 204° C. for 2 hours and (6) 232° C. for 16 hours. A resistive layer(˜3 mil) consisting of 5% by weight ACCUFLUOR® 2028 in VITON® GF wasformed. The surface resistivity of the layer was measured according tothe procedures of Example I and was found to be approximately 1×10⁸ohm/sq.

Example VIII

A resistive layer containing of 5% by weight ACCUFLUOR® 2028 in VITON®GF was prepared according to the procedures in Example VII, with theexception that 1.36 g of DIAK 1 was used as the curative. The surfaceresistivity of the layer was measured at 1×10⁵ ohm/sq.

Example IX

A coating dispersion was prepared by first adding a solvent (200 g ofmethyl ethyl ketone), a steel shot (2300 g) and 1.4 g of ACCUFLUOR® 2028in a small bench top attritor (model 01A). The mixture was stirred forabout one minute so that the fluorinated carbon became wet. A polymerbinder, VITON® GF (45 g), was then added and the resulting mixture wasattrited for 30 minutes. A curative package (1.36 g DIAK 3 and 0.2 gMaglite Y) and a stabilizing solvent (10 g methanol) were thenintroduced and the resulting mixture was further mixed for another 15minutes. After filtering the steel shot through a wire screen, thefluorinated carbonNITON® GF dispersion was collected in a polypropylenebottle. The dispersion was then coated onto KAPTON® substrates within2-4 hours using a Gardner Laboratory coater. The coated layers werefirst air-dried for approximately 2 hours and then heat cured in aprogrammable oven. The heat curing sequence was: (1) 65° C. for 4 hours,(2) 93° C. (3) 144° C. for 2 hours. (4) 177° C. for 2 hours, (5) 204° C.for 2 hours and (6) 232° C. for 16 hours. A resistive layer (˜3 mil)consisting of 3% ACCUFLUOR® 2028 in VITON® GF was formed. The surfaceresistivity of the layer was approximately 8×10⁶ ohm/sq.

Example X

Resistive layers consisting of 5% ACCUFLUOR® 2028 in VITON® GF wereprepared using the dispersion and coating procedures as outlined inExample VII, with the exception that the curing times and the curingtemperatures were changed. The surface resistivities of these layers aresummarized in Table 5.

                  TABLE 5                                                         ______________________________________                                        Curing Temperature                                                                         Curing time  Surface Resistivity                                 (°C.) (hours)      (ohm/sq)                                            ______________________________________                                        232          2            3.6 × 10.sup.8                                232          4.5          1.2 × 10.sup.8                                232          8            1.0 × 10.sup.8                                195          2            1.9 × 10.sup.10                               195          4.5          6.0 × 10.sup.9                                195          8            7.7 × 10.sup.9                                195          23           3.4 × 10.sup.9                                175          4.5          5.2 × 10.sup.10                               175          23           2.0 × 10.sup.10                               149          8            5.2 × 10.sup.11                               149          23           2.3 × 10.sup.11                               ______________________________________                                    

Example XI

Resistive layers consisting of 3% by weight ACCUFLUOR® 2028 in VITON® GFwere prepared using the dispersion and coating procedures as describedin Example IX, with the exception that the curing times and the curingtemperatures were changed. The surface resistivities of these layers aresummarized in Table 6.

                  TABLE 6                                                         ______________________________________                                        Curing Temperature                                                                         Curing Time  Surface Resistivity                                 (°C.) (hours)      (ohm/sq)                                            ______________________________________                                        235          2.5          8.1 × 10.sup.6                                235          6            8.0 × 10.sup.6                                235          8            8.0 × 10.sup.6                                175          2.5          6.6 × 10.sup.8                                175          6            4 × 10.sup.8                                  175          24           8.8 × 10.sup.7                                149          2.5          1.2 × 10.sup.10                               149          6            7.5 × 10.sup.9                                149          8.5          6.1 × 10.sup.9                                149          24           2.5 × 10.sup.9                                ______________________________________                                    

Example XII

A coating dispersion was prepared by first adding a solvent (200 g ofmethyl isobutyl ketone), a steel shot (2300 g) and 8 g of ACCUFLUOR®2028 in a small bench top attritor (model 01A). The mixture was stirredfor about one minute so that the fluorinated carbon became wet. Apolymer binder, VITON® GF (45 g) was then added and the resultingmixture was attrited for 30 minutes. A curative package (2.4 g DIAK 3and 3 g Maglite Y) was added and the resulting mixture was further mixedfor another 15 minutes. After filtering the steel shot through a wirescreen, the ACCUFLUOR® 2028NITON® GF dispersion was collected in apolypropylene bottle. The dispersion was then air-sprayed onto KAPTON®substrates. After air-drying for 1-2 hours, the layer (2.4 mil) washeated at 175° C. for 3 hours. The surface resistivity and the bulkresistivity were determined as outlined in Example I and are 1.4×10⁷ohm/sq and 1×10⁶ ohm-cm, respectively.

Example XIII

Resistive layers consisting of different fluorinated carbons in VITON®GF were prepared according to the procedures described in Example XII.In addition to the spray-coating, flow-coating was also used in certaindispersions. Flow coating procedures are described in Attorney ReferenceD/96035, U.S. application Ser. No. 08/669,761 filed Jun. 26, 1996,entitled, "LEVELING BLADE FOR FLOW COATING PROCESS FOR MANUFACTURE OFPOLYMERIC PRINTER ROLL AND BELT COMPONENTS;" and Attorney ReferenceD/96036, U.S. application Ser. No. 08/672,493 filed Jun. 26, 1996,entitled, "FLOW COATING PROCESS FOR MANUFACTURE OF POLYMERIC PRINTERROLL AND BELT COMPONENTS." The disclosures of both of these applicationsare hereby incorporated by reference in their entirety.

                  TABLE 7                                                         ______________________________________                                                                Surface                                               Filler in VITON ® GF                                                                     Thickness                                                                              Resistivity                                                                            Bulk Resistivity                             (%)            (mil)    (ohm/sq) (ohm-cm)                                     ______________________________________                                        10% ACCUFLUOR ® 2010                                                      (by spray)     1.6      8 × 10.sup.4                                                                     1 × 10.sup.3                           (by flow-coating)                                                                            2.3      9 × 10.sup.3                                                                     ˜1 × 10.sup.3                    10% ACCUFLUOR ® 2010                                                      4% ACCUFLUOR ® 2028                                                       (by spray)     2.4      1.5 × 10.sup.6                                                                   1 × 10.sup.5                           10% ACCUFLUOR ® 2010                                                      5% ACCUFLUOR ® 2028                                                       (by spray)     1.5      1.2 × 10.sup.6                                                                   1.5 × 10.sup.4                         ______________________________________                                    

Example XIV

A VITON® layer consisting of about 15% by weight of ACCUFLUOR® 2028 wasprepared and heat cured according to the procedures described in ExampleI. The surface resistivity of the layer was determined to be>10¹⁴ ohm/sqand the volume resistivity was found to be ˜1×10¹³ ohm-cm. A goldelectrode (˜800 Å thick, 0-25 inch diameter) was evaporated onto a"sister" sample which was coated onto a stainless steel substrate. TheVITON® GF layer, which is now sandwiched between two electrodes, wassubjected to a current treatment by increasing the applied voltageincrementally up to 750 V/cm. An amount of 10 milliamps of DC currentwas applied to the layer for 10 minutes. The bulk resistivity of thislayer was decreased to ˜5×10¹⁰ ohm-cm.

Example XV

A VITON® GF layer consisting about 30% by weight of ACCUFLUOR® 2028 wasprepared according to the procedures outlined in Example I, except thatthis layer was not heat cured. The surface resistivity was>10¹⁴ ohm/sqand the bulk resistivity was ˜10¹³ ohm-cm. This layer was then subjectedto a current treatment using the procedures set forth in Example XIV. Inthis example, the current treatment lasted for about 2 hours. After thecurrent treatment, the bulk resistivity of the layer decreased to˜1.2×10⁹ ohm-cm.

Example XVI

About 15 g of ACCUFLUOR® 2065 was dispersed in 200 g of methyl ethylketone. A curative package containing 2.25 g of VC 50, 0.9 g Maglite-Dand 0.2 g Ca(OH)₂ was added. After mixing, the solvent was removed in anevaporator and the contents were dried in a vacuum oven, yielding a graypowder sample. When this sample was heated at 235° C. for 16 hours, thecolor of the powder changed from gray to black.

Example XVII

The same procedure in Example XVI was repeated except that ACCUFLUOR®2065 was heated in the absence of the curative package. No change incolor was observed. These two experiments demonstrate that the curativecauses defluorination of ACCUFLUOR® 2065, leading to a less fluorinated,black fluorinated carbon.

While the invention has been described in detail with reference tospecific and preferred embodiments, it will be appreciated that variousmodifications and variations will be apparent to the artisan. All suchmodifications and embodiments as may readily occur to one skilled in theart are intended to be within the scope of the appended claims.

We claim:
 1. A coating comprising a fluorinated carbon filledfluoroelastomer, wherein said fluoroelastomer is selected from the groupconsisting of (i) tetrapolymers of vinylidenefluoride,hexafluoropropylene, tetrafluoroethylene and a cure site monomer, and(ii) volume grafted fluoroelastomers.
 2. A coating in accordance withclaim 1, wherein the fluoroelastomer comprises tetrapolymers ofvinylidenefluoride, hexafluoropropylene, tetrafluoroethylene and a curesite monomer.
 3. A coating in accordance with claim 2, wherein thefluoroelastomer comprises about 35 mole percent of vinylidenefluoride,about 34 mole percent of hexafluoropropylene, about 29 mole percent oftetrafluoroethylene and about 2 mol percent of a cure site monomer.
 4. Acoating in accordance with claim 1, wherein the fluorinated carbon is ofthe formula CF_(x), wherein x represents the number of fluorine atoms.5. A coating in accordance with claim 4, wherein x is a number of fromabout 0.02 to about 1.5.
 6. A coating in accordance with claim 1,wherein the fluorinated carbon is present in an amount of from about 1to about 40 percent by weight based on the weight of total solids.
 7. Acoating in accordance with claim 1, wherein the fluorinated carbon has afluorine content of from about 5 to about 65 weight percent based on theweight of fluorinated carbon, and a carbon content of from about 95 toabout 35 weight percent based on the weight of fluorinated carbon.
 8. Acoating in accordance with claim 1, wherein said fluorinated carbon isselected from the group consisting of a fluorinated carbon having afluorine content of 62 weight percent, a fluorinated carbon having afluorine content of 11 weight percent, a fluorinated carbon having afluorine content of 28 weight percent, and a fluorinated carbon having afluorine content of 65 weight percent based on the weight of fluorinatedcarbon.
 9. A coating in accordance with claim 8, comprised offluorinated carbon having a fluorine content of 28 percent by weight offluorinated carbon, in an amount of from about 1 to about 40 percent byweight of total solids.
 10. A coating in accordance with claim 8,comprised of fluorinated carbon having a fluorine content of 11 percentby weight of fluorinated carbon, in an amount of from about 1 to about40 percent by weight of total solids.
 11. A coating in accordance withclaim 8, comprised of a mixture of fluorinated carbons, wherein themixture comprises a fluorinated carbon having a fluorine content of 28percent by weight of fluorinated carbon, in an amount of from about 1 toabout 35 percent by weight of total solids, and a fluorinated carbonhaving a fluorine content of 11 weight percent by weight of fluorinatedcarbon, in an amount of from about 1 to about 35 percent by weight oftotal solids.
 12. A coating in accordance with claim 11, comprised of amixture of fluorinated carbons, wherein the mixture comprises afluorinated carbon having a fluorine content of 28 percent by weight offluorinated carbon, in an amount of from about 1 to about 3 percent byweight of total solids, and a fluorinated carbon having a fluorinecontent of 11 weight percent by weight of fluorinated carbon, in anamount of from about 2.5 to about 3.5 percent by weight of total solids.13. A coating in accordance with claim 8, comprised of a mixture offluorinated carbons, wherein the mixture comprises a fluorinated carbonhaving a fluorine content of 62 percent by weight of fluorinated carbon,in an amount of from about 1 to about 40 percent by weight of totalsolids, and a fluorinated carbon having a fluorine content of 65 percentby weight of fluorinated carbon, in an amount of from about 1 to about40 percent by weight of total solids.
 14. A coating in accordance withclaim 1, wherein the fluoroelastomer is present in an amount of fromabout 60 to about 99 percent by weight based on the weight of totalsolids.
 15. A coating in accordance with claim 1, wherein the coatinghas a volume resistivity of from about 10² to about 10¹⁴ ohm-cm.
 16. Acoating in accordance with claim 15, wherein the coating has a volumeresistivity of from about 10³ to about 10¹² ohm-cm.
 17. A coating inaccordance with claim 1, wherein said fluoroelastomer is a volumegrafted fluoroelastomer.
 18. A coating in accordance with claim 1,wherein said fluorinated carbon filled fluoroelastomer is cured.
 19. Acoating of claim 1 wherein said coating has a controlled resistivity.20. A coating in accordance with claim 19, wherein said coating has afirst resistivity and a second resistivity, wherein said firstresistivity is a resistivity of said coating at room temperature, andwherein said second resistivity is a resistivity of said coating upon achange in temperature, wherein said second resistivity remains withinabout 50 to about 100% of said first resistivity at a temperature rangeof from about 0° to about 200° C.
 21. A coating in accordance with claim20, wherein said room temperature is about 25° C.
 22. A coating inaccordance with claim 19, wherein said coating has a first resistivityand a second resistivity, wherein said first resistivity is aresistivity of said coating at ambient relative humidity, and whereinsaid second resistivity is a resistivity of said coating upon a changein relative humidity, wherein said second resistivity remains withinabout 50 to about 100% of said first resistivity at a relative humidityrange of from about 0% to about 80% relative humidity.
 23. A coating inaccordance with claim 22, wherein said ambient relative humidity isabout 50% relative humidity.
 24. A coating in accordance with claim 1,wherein said fluoroelastomer comprises 35 mole percentvinylidenefluoride, 34 mole percent hexafluoropropylene, 29 mole percenttetrafluoroethylene, and 2 mole percent cure site monomer.